The invention is directed to a high speed ion beam switching arrangement for use in the production of determinate solid body dopings by means of ion implantation, particularly in semiconductor material.
A determinate doping of the semiconductor material of semiconductor components is necessary if reproduceable results are to be achieved in production. While the control of the dose of a dopant implanted in a solid body can take place within wide dose ranges in known ion current integrators, considerable problems arise in connection with the exact termination of the ion implantation when the desired dose has been achieved, under control of an output signal from the ion current integrator. This was particularly true when, for reasons of economy, determinate implantation results, i.e. dopings, were to be achieved in short implantation times.
The following described processes have been followed, in accordance with the current prior art, in connection with the effecting of a predetermined implantation dose.
In one known process, a mechanically movable diaphragm, at the beginning of the implantation process, exposes the solid body which is to be implanted for bombardment, with such bombardment being terminated by again covering the body. The process can be automatically controlled by an ion current integrator of known construction. The sequence, however, is fairly long and inaccurate as the diaphragm posesses a certain minimum mass whereby it will not be unduly heated during the closed condition by the energy supplied by impacting ions.
In accordance with another known process, the ion beam is guided into the direction of bombardment by means of an electric voltage operatively connected to two capacitive deflector plates at the beginning of the implantation, and is diverted therefrom to effect a termination of the bombardment. The electric voltage connected to the deflector capacitor plates is dependent upon the ion energy, and must be matched to the latter whereby, in the case of high ion energies, may assume impractically high values i.e. 20 kV and above. This is particularly the case when the deflector capacitor is, as is usual, disposed at a location following the main ion acceleration section. Although this known arrangement permits short disconnection times, it has the disadvantage that during the disconnection state the ions hit some parts of the apparatus, whereby such ions, as a result of surface sputtering, additionally pollute the vacuum and therefore may lead to an undesired contamination of the solid bodies which are to be doped.
It is the objective of the present invention to provide an arrangement for high speed ion beam disconnection by means of which it is possible to achieve a sharply timed definite ion implantation, and in which disadvantages such as those above described with respect to the prior art eliminated.